The way in which Willi Hennig and Peter Ax substantiated hypotheses on character polarity are described and compared to the presently most common practice of polarising characters by rooting an unrooted network. Although Hennig applied the outgroup comparison method implicitly, and Ax regarded this method as the only general and reliable tool for determining character polarity, there is a crucial difference to the application of this method in present-day mainstream cladistics: Traditionally (Hennig, Ax), character polarity was assessed on a character-by-character basis, while in ‘present-day mainstream cladistics’ rooting replaced the a-priori-discussion of possible character transformations.